Negative Electrode Binder Gradient for Faster Li-Ion Migration
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Solution Overview
Problem
Secondary batteries, such as lithium-ion batteries, face challenges in achieving higher kinetic performance, including shorter charging times and improved cycle life, due to limitations in lithium ion migration and electrode stability.
Innovation Solution
A secondary battery design featuring a negative electrode plate with a first active layer and a second active layer, both doped with a negative electrode binder, where the binder's mass percentage varies to enhance bonding strength and reduce lithium ion concentration on the surface, allowing for direct application without an undercoat, thereby improving energy density and kinetic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the content of negative electrode binder in the second active layer is increased to improve bonding strength, then electrode stability is improved, but lithium ion migration speed decreases and kinetic performance deteriorates
Solution Approach 1:
The patent applies different binder contents to different regions of the negative electrode plate. The first active layer (near current collector) contains 1.0-3.0 wt% binder for strong bonding, while the second active layer (outer layer) contains 0.05-0.65 wt% binder to minimize lithium ion migration resistance. This local differentiation resolves the contradiction by optimizing each region's binder content for its specific function.
2Strength
If an undercoat is added to improve bonding between active layer and current collector, then bonding strength is improved, but electrode plate thickness and battery volume increase
Solution Approach 1:
The patent merges the bonding function with the first active layer itself. By setting the binder content in the first active layer to 1.0-3.0 wt%, the layer simultaneously serves as both the active material layer and the bonding layer, eliminating the need for a separate undercoat while maintaining strong adhesion to the current collector.
3Quantity of substance
If the thickness of negative electrode plate is reduced to improve energy density, then energy density is improved, but lithium ion migration distance increases and kinetic performance deteriorates
Solution Approach 1:
The patent creates a gradient structure where the first active layer near the current collector has higher binder content (1.0-3.0 wt%) providing strong bonding and facilitating lithium ion entry, while the second active layer has lower binder content (0.05-0.65 wt%) minimizing migration resistance. This local optimization allows thin electrode design with high energy density while maintaining fast kinetic performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design accelerates lithium ion migration, reduces lithium plating, and enhances cycle performance, resulting in shorter charging times and increased energy density.
Implementation Method 1
accelerating migration of lithium ions into the active material particles and into the active material layer
Implementation Method 2
The negative electrode binder includes a polymer formed by emulsion polymerization of styrene, acrylate ester, and acrylic acid
Data Source
AI summary
A secondary battery includes a negative electrode plate. The negative electrode plate includes a negative current collector, a first active layer, and a second active layer. The first active layer is disposed between the negative current collector and the second active layer. In a thermogravimetric analysis, a weight loss rate of the first active layer in a temperature range of 350° C. to 500° C. is 1.3% to 3.0%, and a weight loss rate of the second active layer in a temperature range of 350° C. to 500° C. is 0.05% to 0.65%. Such settings can improve the kinetic performance of the secondary battery.